Labyrinthitis deals with the material science of sound — in particular the Tartini tone.
As you'll recall, sound is a wave. Imagine this wave drawn on an XY axis and then another wave drawn over or around that first wave. One can add together the peaks of the two waves to create another. This third wave, when it is realized in sound, is (drum roll) the Tartini tone. When these superimposed sounds (the most effective are sine waves) get played into the ear, the ear vibrates at the third (and sometimes fourth and fifth) additive frequency and thereby "creates" a new sound within the ear itself.
Kirkegaard began this project by finding the Tartini tones that his ears created in response to certain waves. He then layered these into the composition, so you're never sure whether your ears are hearing the sounds or creating them. It's all less clinical than you might expect, and Kirkegaard keeps the music lively by shifting from simple sine waves to busier, sparkling layers that I may or may not be, get this, creating in my ear, man!